Gut morphology and blood biochemical parameters of growing pigs fed diets with a partial to total replacement of soybean meal with Arthrospira platensis

Diana Giannuzzi^1,2Alessandro Toscano^1,2Gregorio Don^1,2*Rina Verdiglione^1,2Schiavon Stefano^1,2Luigi Gallo^1,2

• ¹Universita degli Studi di Padova Dipartimento di Agronomia Animali Alimenti Risorse naturali e Ambiente, Legnaro, Italy
• ²University of Padua, Padua, Italy

Soybean meal is the main protein source in pig diets, but its production has been associated to deforestation, soil degradation and loss of biodiversity. Arthrospira platensis (AP), a protein-rich cyanobacterium with a favourable amino acid profile, might represent a sustainable alternative. This study aimed to assess the impact of a partial to full replacement of soybean meal with AP on gut morphology and blood biochemical parameters in growing-finishing pigs. Eighty-eight barrows and gilts were assigned to one of four isoenergetic, isoproteic, and isoaminoacidic diets: control (100% soybean meal as protein source), and experimental diets replacing 33%, 66%, or 100% of soybean meal with AP. Individual blood samples were collected at the start of the trial (91 days), and prior to slaughter (238 days), when pigs’ body weight averaged 41±3 kg and 175±6 kg, respectively. Ileum and colon tissues were sampled at slaughterhouse for histological analysis and evaluation of gut morphology. Across dietary treatments, biochemical profiling indicated metabolic, oxidative, and inflammatory stability, with no alterations in liver or kidney related parameters. Consistently, histological evaluation indicated that intestinal architecture was preserved across all the dietary treatments, even though ileal villus width and crypt depth tended to increase linearly with higher dietary inclusion of AP, and a similar trend was observed for ileal inflammation score. Despite reports in other species suggesting AP antioxidative and anti-inflammatory benefits, these were not evident in pigs under the conditions tested. Nonetheless, the absence of adverse effects on intestinal and systemic health supports the nutritional viability of AP as a complete replacement for soybean meal. These findings highlight its potential as a sustainable and safe protein source in swine production without compromising physiological status or gut health.